this is the code that generate the exception:

try:
    backup = open(BACKUP_DIR + '/' + backups_in_folder[-1], 'rb')
    file_size = os.path.getsize(BACKUP_DIR + '/' + backups_in_folder[-1])
    CHUNK_SIZE = 4 * 1024 * 1024
    dbx = dropbox.Dropbox(DROPBOX_UPLOAD_ACCESSKEY)
    if file_size <= CHUNK_SIZE:
        dbx.files_upload(backup, '/' + backups_in_folder[-1])
    else:
        upload_session_start_result = dbx.files_upload_session_start(backup.read(CHUNK_SIZE))
        cursor = files.UploadSessionCursor(session_id=upload_session_start_result.session_id, offset=backup.tell())
        commit = files.CommitInfo(path='/' + backups_in_folder[-1])

        while backup.tell() < file_size:
            if (file_size - backup.tell()) <= CHUNK_SIZE:
                dbx.files_upload_session_finish(backup.read(CHUNK_SIZE), cursor, commit)
            else:
                dbx.files_upload_session_append(backup.read(CHUNK_SIZE), cursor.session_id, cursor.offset)
                cursor.offset = backup.tell()

except Exception, e:
    print('* ERROR:' + str(e))

Hi Sergio, is this happening on every API call, or only some of them? If it's only some of them, about what percent?